Recuperação de estruturas na tuba uterina após transferência intrafolicular de oócitos imaturos (tifoi) com diferente número de complexo cumulus-oócito injetados

Abstract

Many factors may be involved in the low efficiency of IFIOT and to identify these factors, it is necessary to clarify in which point of the process the greatest losses are occurring. The aim was to evaluate the effect of the amount of COC injected during IFIOT on recovery rate of structures and embryos in the oviduct. Were used 45 non- lactating cows, submitted an ovulation synchronization protocol (D0: P4+2mg EB; D8:0,5mg PGF and removal P4 device; D9: 1mg EB). At 54.5±2.7h after removal the P4 device, IFIOT was performed: Control Group (CG; n=15): IFIOT with injection of 60μL of medium (TCM199) plus 10% FBS), without the presence of CCO; Group 5 (G5; n=15): IFIOT with injection of 5 CCO in 60μL of medium; Group 50 (G50; n=15): IFIOT with injection of 50 CCO in 60μL of medium. After IFIOT, cows were inseminated and received 10μg of buserelin acetate i.m. (GnRH; Sincroforte®). Between 64 - 66 hours after IFIOT, slaughter was carried out to collect the reproductive tract, with dissection and washing of the oviduct ipsilateral to the ovary that presented ovulation. Oviduct washing was performed with 3 mL of PBS and the content evaluated for the presence of structures. Were considered structures: unfertilized oocytes, zona pellucida or embryos (cleaved oocytes). After washing, the oviduct was divided into four fragments and collected for histology in order to evaluate the presence of inflammatory cells. According to recovery, the animals were allocated to the following groups: no structure present in the oviduct (Histo0, n = 11); 01 structure present in the oviduct (Histo1, n = 16); 2-9 structures present in the oviduct (Histo2-9, n = 8); and 11-40 structures present in the oviduct (Histo11-40, n = 10). To assess whether the injected and unrecovered COC in the oviduct would be retained in the follicle after ovulation, the forming CL was dissected, and internal cavity was washed. To calculate the recovery rate of total structures and embryos, one structure was removed in order to disregard the physiological structure from the follicle of the "ovulator” cow. The total recovery and embryos rate between groups were compared using the Mann-Whitney test (P<0.05). The structures recovery rate and embryos were submitted to Pearson's correlation with the follicular diameter (FD); dominant follicle perfusion on D10; time interval of permanence of CCO in the injection needle and oviduct size. Descriptively, after oviduct washing the CG, 11 (73.3%) cows presented a structure, with 72.7% of cleaved. In G5 and G50 was recovered structures in 10 (66.7%) and 13 (86.7%) cows, respectively. Considering the presence of ≥2 structures, the recovery occurred in 7 (46.7%) and 10 (66.7%) cows, for G5 and G50, respectively. The recovery rate of total structures and embryos was similar between G5 (24%; 9.3%) and G50 (31.6%; 7.0%). Finally, in 2 (13.3%) and 7 (45.6%) animals from G5 (2.7%) and G50 (2.1%) oocytes were recovered after CL dissection. No correlation was found between the recovery rate of total and cleaved structures with any parameters evaluated: FD diameter (R=- 0.1 and R=0.32); dominant follicle perfusion (R=-0,03 e R=-0,05); oviduct length (R=- 0.11 and R=-0.17) and length stay of the oocyte on the needle (R=-0.05 and R=-0.05). Regardless of the amount of COCs recovered, no difference was observed in the amount of inflammatory cells in the different segments of the tube. However, in the Histo0 and Histo11-40 groups, the proximal ampulla portion showed a greater amount (P>0.05) of inflammatory cells when compared to the distal isthmus. In the Histo1 group, the proximal and distal ampulla had a greater amount of inflammatory cells than in the isthmus segments. The presence of COC was not observed in the CL samples. These results suggest that the low recovery may not be in the uptake, but in the release of these COCs at the time of ovulation.